What Is a Liquid Level Electrode? Types and Selection Criteria
A liquid level electrode is a metal sensing probe hung by its cable into a tank that signals a liquid level relay when it touches a conductive liquid.
A liquid level electrode is a metal sensing probe hung by its cable into a tank or well that signals the liquid level relay it is connected to when it touches a conductive liquid. The electrode does not switch anything itself; when the liquid bridges two electrodes, the relay detects the small current and controls a pump or an alarm. It is used in tank filling, well and drainage emptying and dry-run protection circuits for pumps.
How many electrodes are needed?
| Electrode | Function |
|---|---|
| Common electrode | Nearest the bottom of the tank; always stays in the liquid |
| Low level electrode | Tells the relay "empty" when the level drops below it |
| High level electrode | Tells the relay "full" when the level reaches it |
A single-tank filling or emptying circuit usually uses three electrodes. For dry-run protection a second set of electrodes goes into the well or lower tank. Check the relay's datasheet for how many electrode inputs it has.
Selection criteria
- Liquid: The electrode works only in electrically conductive liquids (such as mains, well and waste water). For pure (distilled or deionised) water, oil and fuel, a float switch is used.
- Material: The product data gives stainless steel for the electrodes in the catalog. In acidic or chemical liquids, confirm material compatibility with the manufacturer.
- Size: The Entes LLS-01 is sold as small and the LLS-02 as large; compare the dimensions of the Tense SSE-10 and SSE-20 on the product pages. A small body passes more easily through narrow pipes and well openings.
- Cable: The electrode cable works in a wet environment, so its outer sheath must be water-resistant. On long runs, cable resistance and leakage affect the relay's sensitivity setting; set it again at commissioning.
- Position: Hang the electrodes away from the tank wall, from each other and from the inflow at the filling point, at different lengths for each level point.
Common mistakes
- Electrodes touching each other or a metal pipe: The relay behaves as if liquid were present, so the pump does not stop or does not start.
- Leaving the common electrode too short: When the level drops, the common electrode is left in the air and the relay cannot see any level.
- Not cleaning off scale and deposits: Contact weakens on a coated electrode; check and clean the electrodes periodically.
Liquid level electrodes at Welibaba
The Liquid Level Control Electrodes category has 4 active products, all listed with prices: Entes LLS-01 (small) and LLS-02 (large), and Tense SSE-10 and SSE-20. For a comparison of electrodes, float switches and other parts, see the liquid level control accessories guide.
Frequently asked questions
Does a liquid level electrode work on its own?
No. The electrode is only the probe that touches the liquid; the liquid level relay evaluates the level and controls the pump.
How many electrodes does a tank need?
Usually three for filling or emptying: common, low level and high level. If dry-run protection is also wanted, separate electrodes are added in the well or lower tank.
How deep are the electrodes hung?
The common electrode goes lowest, the low level electrode at the level where the pump should start or stop, and the high level electrode at the full level. The gap between high and low keeps the pump from starting and stopping too often.